The generation of symbols for printing or display by selecting predetermined groups of dots from a set matrix or potential dots is a highly developed art. This technique has been used in various forms for cathode ray tube type computer output terminals, computer line printers and graphics quality photocomposers, and telegraphic printers, to mention a few examples.
The conventional dot printing mechanism normally operates in a single, fixed mode to produce alpha numeric characters of uniform height and selected shape. Earlier attempts at changing the fixed format to a more flexible arrangement which would permit printing of various character type fronts have been unduly limited in the variety of print size, choice of printed character, and flexibility made available; further, such variations often were found to be lacking in clarity of the printed elements. Such clarity is significant for aesthetic purposes and for ease of reading, but it was found to be even more important where such printers were used in the printing of product bar codes, and the like, where the clarity of the printing had to meet the requirements of optical readers. Prior systems for using dot printers were found to be inadequate both from the aesthetic point of view, and bcause they were not capable of accurate production of printed material such as bar codes. Further, the prior control devices caused the printers to operate at relatively slow speeds, and in order to produce differently sized characters beside each other, it was necessary to pass the page through the printer once for each individual size of character.